Assessment of municipal wastewaters at various stages of treatment process as potential growth media for Chlorella sorokiniana under different modes of cultivation Prathana Ramsundar, Abhishek Guldhe, Poonam Singh, Faizal Bux ⇑ Institute for Water and Wastewater Technology, Durban University of Technology, P.O. Box 1334, Durban 4000, South Africa highlights  Anaerobic centrate and influent were suitable growth medium for microalgae.  Filtration was most feasible pre-treatment for bacterial reduction.  High biomass productivity found in anaerobic centrate.  Mixotrophic mode was most suitable cultivation strategy for domestic wastewater.  Urea supplementation improved biomass and metabolites productivities. article info Article history: Received 16 September 2016 Received in revised form 9 December 2016 Accepted 11 December 2016 Available online 18 December 2016 Keywords: Microalgae Wastewater Heterotrophic Mixotrophic Biomass abstract Wastewater utilization for microalgal biomass production is potentially the most economical route for its fuel and feed applications. In this study, suitability of various wastewater streams within a domestic wastewater treatment plant was evaluated for microalgal cultivation. Pre-treatment methods were eval- uated to minimize bacterial load. Biomass, cell physiology, nutrient removal efficiencies and biochemical constituents of Chlorella sorokiniana were investigated in influent (INF) and anaerobic tank centrate (AC) under mixotrophic (Mixo) and heterotrophic (Hetero) cultivation. Promising biomass (77.14 mg L 1 d 1 ), lipid (24.91 mg L 1 d 1 ), protein (22.36 mg L 1 d 1 ) and carbohydrate (20.10 mg L 1 d 1 ) productivities were observed in Mixo AC with efficient ammonium (94.29%) and phosphate (83.30%) removal. Supplementation of urea at a concentration of 1500 mg L 1 further enhanced biomass (162.50 mg L 1 d 1 ), lipid (24.91 mg L 1 d 1 ), protein (22.36 mg L 1 d 1 ) and carbohydrate (20.10 mg L 1 d 1 ) productivities in Mixo AC. Urea supplemented mixotrophic cultivation of microalgae in AC is developed as a biomass production strategy. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction Microalgal biomass has been put forth as a promising feedstock for biofuels, animal feed, aquaculture, cosmetics, nutraceuticals and biofertilizer industries (Mata et al., 2014). To make these appli- cations sustainable and economical, microalgal biomass needs to be produced on a commercial scale with minimal production cost. Microalgal biomass production is successfully applied on relatively small-scale systems, generally for nutraceuticals and anthro- pogenic consumption which are high value commodities (Benemann, 2013). The worldwide production of microalgal biomass does not exceed more than 15 000 tons per annum at a production cost of at least 10 €kg 1 (Morales-Amaral et al., 2015). The requirement of large amounts of microalgae-essential macronutrients i.e., nitrogen (N) and phosphorous (P), in addition to carbon dioxide (CO 2 ), is one of the major reason for high produc- tion cost (Morales-Amaral et al., 2015). In order to alleviate this problem microalgae cultivation using waste materials as opposed to synthetic media has been antici- pated, mainly with regard to wastewater reuse and treatment. Wastewater contains a combination of organic matter, nutrients and synthetic compounds. Wastewater contains majority of the nutrients required for microalgal cultivation and thus can be used for biomass production. Discharge of these wastewaters leads to the problem of eutrophication or algal blooms into receiving waters (Morales-Amaral et al., 2015). http://dx.doi.org/10.1016/j.biortech.2016.12.037 0960-8524/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: faizalb@dut.ac.za (F. Bux). Bioresource Technology 227 (2017) 82–92 Contents lists available at ScienceDirect Bioresource Technology journal homepage: www.elsevier.com/locate/biortech